Fix flake8 errors

[ovuolteenaho]

Assigned to Teemu for now, he can delegate this forward.

$ flake8
./abusehelper/bots/archivebot/archivebot.py:91:5: E722 do not use bare except'
./abusehelper/core/bot.py:319:13: E722 do not use bare except'
./abusehelper/core/imapbot.py:192:9: E722 do not use bare except'
./abusehelper/core/log.py:37:9: E722 do not use bare except'
./abusehelper/core/roomgraph.py:222:13: E722 do not use bare except'
./abusehelper/core/runtime.py:152:9: E722 do not use bare except'
./abusehelper/core/services.py:288:13: E722 do not use bare except'
./abusehelper/core/services.py:350:13: E722 do not use bare except'
./abusehelper/core/startup.py:259:9: E722 do not use bare except'
./abusehelper/core/mailer.py:127:17: E722 do not use bare except'
./abusehelper/core/mail/imapbot.py:179:9: E722 do not use bare except'
./abusehelper/core/tests/test_utils.py:109:5: E722 do not use bare except'

These are soon ignored in tox.ini, so please remove E722 after fixing:

[flake8]
ignore = E501,E722